The present invention relates to a light-beam deflecting apparatus, in which a polygon mirror is pushed against a flange to hold it stationary, a manufacturing method of the light-beam deflecting apparatus and an image-forming apparatus.
Conventionally, electro-photographic image-forming apparatuses, such as laser-beam printers, digital copiers, etc., have employed a light-beam deflecting apparatus for scanning a light-beam, in order to write images onto a photoreceptor drum. In the conventional light beam deflection apparatus, a polygon mirror combined with magnets is rotatably inserted into a central axis of the base body with a bearing between them, and driving coils are disposed opposite the magnets so that a rotational torque, caused by the relative magnetic forces generated between the permanent magnets and the driving coils when electric currents flow into the driving coils, rotates the polygon mirror at a high rate, while forming an air gap between the base body and a rotating disk including the polygon mirror, etc.
In the abovementioned light-beam deflecting apparatus, since the polygon mirror is pushed against the flange to hold it stationary relative to the flange, contacting surfaces of both the polygon mirror and the flange should be finished as accurate surfaces to improve an inclined angle of a mirror surface of the polygon mirror. Such contacting surfaces are finished so that their surface roughness Ry is not greater than 1 xcexcm (Ryxe2x89xa61 xcexcm). In the conventional configuration, however, in which both the contacting surfaces push against each other to fix the polygon mirror onto the flange, there has been a fear that the position of the polygon mirror possibly deviates from its original position due to a centrifugal force generated by high-speed rotation, resulting in unbalance of the mass distribution of the rotating disk and an increase of vibrations.
To overcome the abovementioned drawbacks in the conventional light-beam deflecting apparatus, it is an object of the present invention to provide a light-beam deflecting apparatus which makes it possible to prevent the polygon mirror from deviating from the original position and to stably rotate the polygon mirror, even if the polygon mirror, pushed against the flange, rotates at a high rate during its operating time. It is also an object of the present invention to provide a method for manufacturing such light-beam deflecting apparatus, and further to provide an image-forming apparatus equipped with such light-beam deflecting apparatus.
Accordingly, to overcome the cited shortcomings, the abovementioned object of the present invention can be attained by a light-beam deflecting apparatus, methods for manufacturing the light-beam deflecting apparatus and image-forming apparatus described as follows.
(1) A light-beam deflecting apparatus, comprising: a base member; a polygon mirror being rotatable in respect to the base member; a flange contacting the polygon mirror to hold the polygon mirror; and a pushing member to push the polygon mirror against the flange; wherein one or both of contacting surfaces of the polygon mirror and the flange is/are finished to a surface roughness of Ry, which fulfills a first formula of Ryxe2x89xa73 xcexcm.
(2) The light-beam deflecting apparatus of item 1, wherein surface roughness Ry fulfills a second formula of 3 xcexcmxe2x89xa6Ryxe2x89xa620 xcexcm.
(3) The light-beam deflecting apparatus of item 1, wherein one or both of contacting surfaces of the polygon mirror and the flange is/are finished to surface roughness Ry, by employing one of an abrasive blasting, a cutting machining, a laser machining, a dry ice blasting, a chemical processing and a form rolling, or by employing a combination of a plurality of machining methods arbitrarily selected from them.
(4) A method for manufacturing a light-beam deflecting apparatus, which incorporates a polygon mirror being rotatable in respect to a base member and a flange contacting the polygon mirror to hold the polygon mirror, comprising the steps of: finishing one or both of contacting surfaces of the polygon mirror and the flange to a surface roughness of Ry, which fulfills a first formula of Ryxe2x89xa73 xcexcm; and fixing the polygon mirror onto the flange by pushing the polygon mirror against the flange so that both of the contacting surfaces contact each other with a pushing force applied, in order to assemble the light-beam deflecting apparatus.
(5) The method of item 4, wherein surface roughness Ry fulfills a second formula of 3 xcexcmxe2x89xa6Ryxe2x89xa620 xcexcm.
(6) The method of item 4, wherein one or both of the contacting surfaces is/are finished to surface roughness Ry, by employing one of an abrasive blasting, a cutting machining, a laser machining, a dry ice blasting, a chemical processing and a form rolling, or by employing a combination of a plurality of machining methods arbitrarily selected from them.
(7) The method of item 4, wherein one or both of the contacting surfaces is/are finished to surface roughness Ry, which fulfills a third formula of Ry less than 3 xcexcm, before performing the finishing step.
(8) An image-forming apparatus, comprising: a photoreceptor; and the light-beam deflecting apparatus cited in item 1; wherein a light-beam, reflected from the polygon mirror, writes image information on the photoreceptor.
(9) The image-forming apparatus of item 8, wherein surface roughness Ry fulfills a second formula of 3 xcexcmxe2x89xa6Ryxe2x89xa620 xcexcm.
(10) The image-forming apparatus of item 8, wherein one or both of contacting surfaces of the polygon mirror and the flange is/are finished to surface roughness Ry, by employing one of an abrasive blasting, a cutting machining, a laser machining, a dry ice blasting, a chemical processing and a form rolling, or by employing a combination of a plurality of machining methods arbitrarily selected from them.
Further, to overcome the abovementioned problems, another light-beam deflecting apparatus and methods for manufacturing such light-beam deflecting apparatus, embodied in the present invention, will be described as follows:
(11) A light-beam deflecting apparatus, characterized in that, a base member, a polygon mirror rotating in respect to the base member, a flange contacting the polygon mirror to hold the polygon mirror and a pushing member to push the polygon mirror against the flange are provided, and a surface roughness (Ry) of one or both of contacting surfaces of the polygon mirror and the flange fulfills Ryxe2x89xa73 xcexcm.
According to the abovementioned light-beam deflecting apparatus, since a surface roughness (Ry) of at least one of contacting surfaces of the polygon mirror and the flange fulfills Ryxe2x89xa73 xcexcm, the frictional force between the contacting surfaces sufficiently increases when the polygon mirror is pushed against the flange to hold the polygon mirror, and thereby, the positional deviation of the polygon mirror, caused by the centrifugal force due to its high-speed rotating action during its operating time, hardly occurs, resulting in the stable rotation of the rotating disk without changing its vibration mode. Incidentally, in the present specification, the term of xe2x80x9csurface roughness (Ry)xe2x80x9d indicates the maximum height defined by JIS-B-0601.
It is desirable that the surface roughness (Ry) of the contacting surface fulfills the formula of 3 xcexcmxe2x89xa6Ryxe2x89xa620 xcexcm. When the surface roughness (Ry) fulfills Ry xe2x89xa620 xcexcm, it is possible to maintain the unit characteristics of the light-beam deflecting apparatus, such as the inclination angle of the mirror surface of the polygon mirror, etc., in an appropriate state. Further, the contacting surface can be finished to the abovementioned surface roughness (Ry), by employing one of an abrasive blasting, a cutting machining, a laser machining, a dry ice blasting, a chemical processing and a form rolling.
(12) A method for manufacturing a light-beam deflecting apparatus, characterized in that the method includes a process for finishing one or both of contacting surfaces of a polygon mirror, rotating in respect to a base member, and a flange, contacting the polygon mirror to hold the polygon mirror, to a surface roughness of Ry, which fulfills Ryxe2x89xa73 xcexcm or desirably 3 xcexcmxe2x89xa6Ryxe2x89xa620 xcexcm, and an assembling process for fixing the polygon mirror onto the flange by contacting their contacting surfaces cc each other and by applying a pushing force to them.
According to the manufacturing method mentioned above, since the polygon mirror is fixed onto the flange by contacting the contacting surfaces of them each other and by applying a pushing force to them in its assembling process, after at least one of the contacting surfaces is finished to a surface roughness of Ryxe2x89xa73 xcexcm, the frictional force between the contacting surfaces sufficiently increases, and thereby, the positional deviation of the polygon mirror, caused by the centrifugal force due to its high-speed rotating action during its operating time, hardly occurs. Therefore, it becomes possible to manufacture a light-beam deflecting apparatus, in which the polygon mirror can stably rotates without generating any vibrations.
In this case, an abrasive blasting, a cutting machining, a laser machining, a dry ice blasting, a chemical processing or a form rolling can be employed for the surface-finish processing.
Further, it is possible to finish the contacting surface so that its surface roughness (Ky) fulfills Ry less than 3 xcexcm, before performing the above-mentioned surface-finish processing. Of course, it is also applicable that the abovementioned surface-finish processing is performed without finishing the contacting surface to the surface roughness Ry less than 3 xcexcm in advance.
Further, an image-forming apparatus, embodied in the present invention, characterized in that, the abovementioned light-beam deflecting apparatus is provided, and a light-beam, reflected from the polygon mirror, writes image information on the photoreceptor element. According to the image-forming apparatus, since the positional deviation of the polygon mirror, caused by the centrifugal force due to its high-speed rotating action during its operating time, hardly occurs, and the polygon mirror can stably rotates without generating any vibrations, it becomes possible to perform a stable image-forming operation for a long time. In addition, since the inclination angle of the mirror surface of the polygon mirror, as well as other characteristics, can be maintained in a desirable state, it becomes possible to contribute to a high-quality image-forming operation.